1. Field of the Invention
The present invention relates to the spraying of mould parting agents and other substances and, more specifically, to apparatus for the automatic, uniform application of a mould parting agent to a die mould in an injection die casting system, and to other spraying equipment.
2. Description of the Prior Art
Injection die casting is generally employed for the mass production of components from thermoplastic synthetics. The thermoplastic mass is extruded in an automatic die casting machine at a high pressure in liquid form through a nozzle into a cooled die casting mould or permanent mould. The process permits the production of components of many different shapes which require little or no subsequent processing.
Frequently the demoulding i.e. the removal of the injection cast components from the die mould presents difficulties. In dependence upon the nature of the synthetic which is used and the shape of the die cast component, said component will remain stuck to the mould and therefore often can be removed from the mould only with much effort. Thus for example components of conical shape can be removed more simply than those having parallel faces or surface lines such as e.g. prismatic or cylindrical components. In dependence upon the nature of the synthetic material it is also possible that the surface of the injection case component which is in contact with the die mould will suffer damage when being removed from the mould.
These difficulties cast doubts upon the question of automation of the demoulding process. It has been proved that the aforementioned difficulties can be successfully overcome by spraying a suitable substance onto the die mould in each case prior to the casting process. Such substances generally known as mould parting agents, are known; thus e.g. zinc stearate which is obtainable in powder form. The substance employed as mould parting agent must be compatible both with the die mould and with the synthetic material employed. In addition the parting agent which is sprayed onto the die mould must uniformly cover the surface of said mould and be able to be applied in a specific concentration. In addition a spraying device is required which will atomize the mould parting agent in such a way that on impact it will be deposited as a thin layer in the mould.
The simplest known spraying devices for manual use are for example the clyster ball, the spray nozzle or the spray gun. These instruments possess substantial disadvantages however, and their use is relatively expensive. Thus it is necessary to intervene into the casting process at specific intervals to exert an operative force on the die casting machine and the die mould must be sprayed with the parting agent. This intervention causes an additional outlay of time in production. As the aforesaid simple devices are also liable to disturbances i.e. generally tend to obstructions of the spray elements such as e.g. the nozzles, uniform spraying of the mould is not guaranteed which has a negative effect on the quality of the die cast components which are produced and can occasionally lead to a high reject quota.